Compositions, layerings, electrodes and methods for making

ABSTRACT

There is a cell comprising an article comprising a hydrocarbon ionomer. The article may be any element in the cell, such as an interior wall, or a modification to an element, such as a film, a membrane, and a coating. The hydrocarbon ionomer is any polymer with ionic functionality, such as a polymeric (methacrylate) neutralized with lithium, and not containing halogen or halogen-containing substituents. The hydrocarbon ionomer may also be included in a composition within an element of the cell, such as a porous separator. The cell also comprises a positive electrode including sulfur compound, a negative electrode, a circuit coupling the positive electrode with the negative electrode, an electrolyte medium and an interior wall of the cell. In addition, there are methods of making the cell and methods of using the cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority on and the benefit of the filing dateof U.S. Provisional Application Nos. 61/587,849, filed on Jan. 18, 2012,and U.S. Provisional Application Nos. 61/602,180, filed on Feb. 23,2012, the entirety of which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

There is significant interest in lithium sulfur (i.e., “Li—S”) batteriesas potential portable power sources for their applicability in differentareas. These areas include emerging areas, such as electrically poweredautomobiles and portable electronic devices, and traditional areas, suchas car ignition batteries. Li—S batteries offer great promise in termsof cost, safety and capacity, especially compared with lithium ionbattery technologies not based on sulfur. For example, elemental sulfuris often used as a source of electroactive sulfur in a Li—S cell of aLi—S battery. The theoretical charge capacity associated withelectroactive sulfur in a Li—S cell based on elemental sulfur is about1,672 mAh/g S. In comparison, a theoretical charge capacity in a lithiumion battery based on a metal oxide is often less than 250 mAh/g metaloxide. For example, the theoretical charge capacity in a lithium ionbattery based on the metal oxide species LiFePO₄ is 176 mAh/g.

A Li—S battery includes one or more electrochemical voltaic Li—S cellswhich derive electrical energy from chemical reactions occurring in thecells. A cell includes at least one positive electrode. When a newpositive electrode is initially incorporated into a Li—S cell, theelectrode includes an amount of sulfur compound incorporated within itsstructure. The sulfur compound includes potentially electroactive sulfurwhich can be utilized in operating the cell. A negative electrode in aLi—S cell commonly includes lithium metal. In general, the cell includesa cell solution with one or more solvents and electrolytes. The cellalso includes one or more porous separators for separating andelectrically isolating the positive electrode from the negativeelectrode, but permitting diffusion to occur between them in the cellsolution. Generally, the positive electrode is coupled to at least onenegative electrode in the same cell. The coupling is commonly through aconductive metallic circuit.

Li—S cell configurations also include, but are not limited to, thosehaving a negative electrode which initially does not include lithiummetal, but includes another material. Examples of these materials aregraphite, silicon-alloy and other metal alloys. Other Li—S cellconfigurations include those with a positive electrode incorporating alithiated sulfur compound, such as lithium sulfide (i.e., Li₂S).

The sulfur chemistry in a Li—S cell involves a related series of sulfurcompounds. During a discharge phase in a Li—S cell, lithium is oxidizedto form lithium ions. At the same time larger or longer chain sulfurcompounds in the cell, such as S₈ and Li₂S₈, are electrochemicallyreduced and converted to smaller or shorter chain sulfur compounds. Ingeneral, the reactions occurring during discharge may be represented bythe following theoretical discharging sequence of the electrochemicalreduction of elemental sulfur to form lithium polysulfides and lithiumsulfide:

S₈→Li₂S₈→Li₂S₆→Li₂S₄→Li₂S₃→Li₂S₂→Li₂S

During a charge phase in a Li—S cell, a reverse process occurs. Thelithium ions are drawn out of the cell solution. These ions may beplated out of the solution and back to a metallic lithium negativeelectrode. The reactions may be represented, generally, by the followingtheoretical charging sequence representing the electrooxidation of thevarious sulfides to elemental sulfur:

Li₂S→Li₂S₂→Li₂S₃→Li₂S₄→Li₂S₆→Li₂S₈→S₈

A common limitation of previously-developed Li—S cells and batteries iscapacity degradation or capacity “fade”. Capacity fade is associatedwith coulombic efficiency, the fraction or percentage of the electricalcharge stored by charging that is recoverable during discharge. It isgenerally believed that capacity fade and coulombic efficiency are due,in part, to sulfur loss through the formation of certain soluble sulfurcompounds which “shuttle” between electrodes in a Li—S cell and react todeposit on the surface of a negative electrode. It is believed thatthese deposited sulfides can obstruct and otherwise foul the surface ofthe negative electrode and may also result in sulfur loss from the totalelectroactive sulfur in the cell. The formation of anode-depositedsulfur compounds involves complex chemistry which is not completelyunderstood.

In addition, low coulombic efficiency is another common limitation ofLi—S cells and batteries. A low coulombic efficiency can be accompaniedby a high self-discharge rate. It is believed that low coulombicefficiency is also a consequence, in part, of the formation of thesoluble sulfur compounds which shuttle between electrodes during chargeand discharge processes in a Li—S cell.

Some previously-developed Li—S cells and batteries have utilized highloadings of sulfur compound in their positive electrodes in attemptingto address the drawbacks associated with capacity degradation andanode-deposited sulfur compounds. However, simply utilizing a higherloading of sulfur compound presents other difficulties, including a lackof adequate containment for the entire amount of sulfur compound in thehigh loading. Furthermore, positive electrodes formed using thesecompositions tend to crack or break. Another difficulty may be due, inpart, to the insulating effect of the higher loading of sulfur compound.The insulating effect may contribute to difficulties in realizing thefull capacity associated with all the potentially electroactive sulfurin the high loading of sulfur compound in a positive electrode of thesepreviously-developed Li—S cell and batteries.

Conventionally, the lack of adequate containment for a high loading ofsulfur compound has been addressed by utilizing higher amounts of binderin compositions incorporated into these positive electrodes. However, apositive electrode incorporating a high binder amount tends to have alower sulfur utilization which, in turn, lowers the effective maximumdischarge capacity of the Li—S cells with these electrodes.

Li—S cells and batteries are desirable based on the high theoreticalcapacities and high theoretical energy densities of the electroactivesulfur in their positive electrodes. However, attaining the fulltheoretical capacities and energy densities remains elusive.Furthermore, as mentioned above, the sulfide shuttling phenomena presentin Li—S cells (i.e., the movement of polysulfides between theelectrodes) can result in relatively low coulombic efficiencies forthese electrochemical cells; and this is typically accompanied byundesirably high self-discharge rates. In addition, the concomitantlimitations associated with capacity degradation, anode-deposited sulfurcompounds and the poor conductivities intrinsic to sulfur compounditself, all of which are associated with previously-developed Li—S cellsand batteries, limits the application and commercial acceptance of Li—Sbatteries as power sources.

Given the foregoing, what is needed are Li—S cells and batteries withoutthe above-identified limitations of previously-developed Li—S cells andbatteries.

BRIEF SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts. Theseconcepts are further described below in the Detailed Description. Thissummary is not intended to identify key features or essential featuresof the claimed subject matter, nor is this summary intended as an aid indetermining the scope of the claimed subject matter.

The present invention meets the above-identified needs by providing Li—Scells incorporating hydrocarbon ionomer articles, such as coatings,membranes, films and other articles incorporating hydrocarbon ionomer.Examples of various types and combinations of hydrocarbon ionomerarticles which may be utilized are described below in the DetailedDescription. The hydrocarbon ionomer articles provide Li—S cells withhigh coulombic efficiencies. In some embodiments, the hydrocarbonionomer articles also provide Li—S cells with high maximum dischargecapacities as well as high coulombic efficiencies, and without theabove-identified limitations of previously-developed Li—S cells andbatteries.

Hydrocarbon ionomer articles, according to the principles of theinvention, provide Li—S cells with surprisingly high coulombicefficiencies and very high ratios of discharge to charge capacity. Whilenot being bound by any particular theory, it is believed that thehydrocarbon ionomer in the hydrocarbon ionomer articles suppresses theshuttling of soluble sulfur compounds and their arrival at negativeelectrodes in the Li—S cells. This reduces capacity fade through sulfurloss in the cells. Furthermore, low sulfur utilization and highdischarge capacity degradation are avoided in these cells.

These and other objects are accomplished by the hydrocarbon ionomerarticles, methods for making such and methods for using such, inaccordance with the principles of the invention.

According to a first principle of the invention, there is a cell. Thecell comprises an article comprising a hydrocarbon ionomer. The cell mayalso comprise one or more of a positive electrode comprising sulfurcompound, a negative electrode, a circuit coupling the positiveelectrode with the negative electrode, an electrolyte medium, and aninterior wall of the cell. The article may be a porous separator. Theporous separator may comprise one or more of polyimide, polyethylene andpolypropylene. The hydrocarbon ionomer may be incorporated as a surfacecoating on a surface of the article in an amount of about 0.0001 to 100mg/cm². The surface coating may be applied by a process comprising acalendaring step. The hydrocarbon ionomer may be a component in apolymer blend incorporated within the porous separator. The hydrocarbonionomer may be located in a pore wall of a pore in the porous separatorand exposed to electrolyte medium in a pore volume in the pore. Theelectrolyte medium may be a lithium-containing cell solution comprisingsolvent and electrolyte. The article may be a coating located on asurface of one or more of a porous substrate, the negative electrode,the circuit, and the interior wall of the cell. The coating may havecharacteristics of a film and be located on a surface of one or more ofthe circuit, and the interior wall of the cell. The coating may havecharacteristics of a membrane and be located on a surface of one or moreat least one of the negative electrode, the circuit, and the interiorwall of the cell. The article may be situated in the electrolyte mediumand be one of a film, a membrane and a combination comprisingcharacteristics of a film and a membrane in different parts of thecombination. The hydrocarbon ionomer may comprise one or more ionicgroup selected from sulfonate, phosphate, phosphonate and carboxylateionic groups. The hydrocarbon ionomer may be a copolymer comprisingabout 5 to 25% by weight ionic comonomer. The hydrocarbon ionomer mayhave a neutralization ratio of greater than about 10%. The hydrocarbonionomer may be at least partially neutralized with lithium. Thehydrocarbon ionomer may be a random copolymer ofpoly(ethylene-co-(meth)acrylic) acid. The copolymer may be at leastpartially neutralized. The copolymer may comprise (meth)acrylic acidcomonomer that is acrylic acid comonomer, methacrylic acid comonomer ora combination of acrylic acid and methacrylic acid comonomers. Thepoly(ethylene-co-(meth)acrylic) acid copolymer may incorporate the(meth)acrylic acid comonomer in an incorporation ratio of less than 20%per mole. The hydrocarbon ionomer may be a neutralized polyvinylsulfonic acid. The hydrocarbon ionomer may be a neutralized sulfonatedderivative of a poly(ether ether-ketone). The article may comprise aplurality of different types of hydrocarbon ionomer.

According to a second principle of the invention, there is a method formaking a cell. The method comprises fabricating a plurality ofcomponents to form the cell. The plurality comprises an articlecomprising a hydrocarbon ionomer. The plurality may also comprise one ormore of a positive electrode comprising sulfur compound, a negativeelectrode, a circuit coupling the positive electrode with the negativeelectrode, an electrolyte medium, and an interior wall of the cell. Thearticle may be a porous separator. The porous separator may comprise oneor more of polyimide, polyethylene and polypropylene. The hydrocarbonionomer may be incorporated as a surface coating on a surface of thearticle in an amount of about 0.0001 to 100 mg/cm². The surface coatingmay be applied by a process comprising a calendaring step. Thehydrocarbon ionomer may be a component in a polymer blend incorporatedwithin the porous separator. The hydrocarbon ionomer may be located in apore wall of a pore in the porous separator and exposed to electrolytemedium in a pore volume in the pore. The electrolyte medium may be alithium-containing cell solution comprising solvent and electrolyte. Thearticle may be a coating located on a surface of one or more of a poroussubstrate, the negative electrode, the circuit, and the interior wall ofthe cell. The coating may have characteristics of a film and be locatedon a surface of one or more of the circuit, and the interior wall of thecell. The coating may have characteristics of a membrane and be locatedon a surface of one or more at least one of the negative electrode, thecircuit, and the interior wall of the cell. The article may be situatedin the electrolyte medium and be one of a film, a membrane and acombination comprising characteristics of a film and a membrane indifferent parts of the combination. The hydrocarbon ionomer may compriseone or more ionic group selected from sulfonate, phosphate, phosphonateand carboxylate ionic groups. The hydrocarbon ionomer may be a copolymercomprising about 5 to 25% by weight ionic comonomer. The hydrocarbonionomer may have a neutralization ratio of greater than about 10%. Thehydrocarbon ionomer may be at least partially neutralized with lithium.The hydrocarbon ionomer may be a random copolymer ofpoly(ethylene-co-(meth)acrylic) acid. The copolymer may be at leastpartially neutralized. The copolymer may comprise (meth)acrylic acidcomonomer that is acrylic acid comonomer, methacrylic acid comonomer ora combination of acrylic acid and methacrylic acid comonomers. Thepoly(ethylene-co-(meth)acrylic) acid copolymer may incorporate the(meth)acrylic acid comonomer in an incorporation ratio of less than 20%per mole. The hydrocarbon ionomer may be a neutralized polyvinylsulfonic acid. The hydrocarbon ionomer may be a neutralized sulfonatedderivative of a poly(ether ether-ketone). The article may comprise aplurality of different types of hydrocarbon ionomer.

According to a third principle of the invention, there is a method forusing a cell. The method comprises one or more steps from the pluralityof steps comprising converting chemical energy stored in the cell intoelectrical energy, and converting electrical energy into chemical energystored in the cell. The cell comprises an article comprising ahydrocarbon ionomer. The cell may also comprise one or more of apositive electrode comprising sulfur compound, a negative electrode, acircuit coupling the positive electrode with the negative electrode, anelectrolyte medium, and an interior wall of the cell. The porousseparator may comprise one or more of polyimide, polyethylene andpolypropylene. The hydrocarbon ionomer may be incorporated as a surfacecoating on a surface of the article in an amount of about 0.0001 to 100mg/cm². The surface coating may be applied by a process comprising acalendaring step. The hydrocarbon ionomer may be a component in apolymer blend incorporated within the porous separator. The hydrocarbonionomer may be located in a pore wall of a pore in the porous separatorand exposed to electrolyte medium in a pore volume in the pore. Theelectrolyte medium may be a lithium-containing cell solution comprisingsolvent and electrolyte. The article may be a coating located on asurface of one or more of a porous substrate, the negative electrode,the circuit, and the interior wall of the cell. The coating may havecharacteristics of a film and be located on a surface of one or more ofthe circuit, and the interior wall of the cell. The coating may havecharacteristics of a membrane and be located on a surface of one or moreat least one of the negative electrode, the circuit, and the interiorwall of the cell. The article may be situated in the electrolyte mediumand be one of a film, a membrane and a combination comprisingcharacteristics of a film and a membrane in different parts of thecombination. The hydrocarbon ionomer may comprise one or more ionicgroup selected from sulfonate, phosphate, phosphonate and carboxylateionic groups. The hydrocarbon ionomer may be a copolymer comprisingabout 5 to 25% by weight ionic comonomer. The hydrocarbon ionomer mayhave a neutralization ratio of greater than about 10%. The hydrocarbonionomer may be at least partially neutralized with lithium. Thehydrocarbon ionomer may be a random copolymer ofpoly(ethylene-co-(meth)acrylic) acid. The copolymer may be at leastpartially neutralized. The copolymer may comprise (meth)acrylic acidcomonomer that is acrylic acid comonomer, methacrylic acid comonomer ora combination of acrylic acid and methacrylic acid comonomers. Thepoly(ethylene-co-(meth)acrylic) acid copolymer may incorporate the(meth)acrylic acid comonomer in an incorporation ratio of less than 20%per mole. The hydrocarbon ionomer may be a neutralized polyvinylsulfonic acid. The hydrocarbon ionomer may be a neutralized sulfonatedderivative of a poly(ether ether-ketone). The article may comprise aplurality of different types of hydrocarbon ionomer.

The above summary is not intended to describe each embodiment or everyimplementation of the present invention. Further features, their natureand various advantages will be more apparent from the accompanyingdrawings and the following detailed description of the examples andembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention become moreapparent from the detailed description set forth below when taken inconjunction with the drawings in which like reference numbers indicateidentical or functionally similar elements. Additionally, the left-mostdigit of a reference number identifies the drawing in which thereference number first appears.

In addition, it should be understood that the drawings in the figures,which highlight the aspects, methodology, functionality and advantagesof the present invention, are presented for example purposes only. Thepresent invention is sufficiently flexible, such that it may beimplemented in ways other than that shown in the accompanying figures.

FIG. 1 is a two-dimensional perspective of a Li—S cell incorporatingseveral hydrocarbon ionomer articles, according to an example;

FIG. 2 is a context diagram illustrating properties of a Li—S batteryincluding a Li—S cell incorporating a hydrocarbon ionomer article,according to an example; and

FIG. 3 is a two-dimensional perspective of a Li—S coin cellincorporating a hydrocarbon ionomer article, according to differentexamples.

DETAILED DESCRIPTION

The present invention is useful for certain energy storage applications,and has been found to be particularly advantageous for high maximumdischarge capacity batteries which operate with high coulombicefficiency utilizing electrochemical voltaic cells which deriveelectrical energy from chemical reactions involving sulfur compounds.While the present invention is not necessarily limited to suchapplications, various aspects of the invention are appreciated through adiscussion of various examples using this context.

For simplicity and illustrative purposes, the present invention isdescribed by referring mainly to embodiments, principles and examplesthereof. In the following description, numerous specific details are setforth in order to provide a thorough understanding of the examples. Itis readily apparent however, that the embodiments may be practicedwithout limitation to these specific details. In other instances, someembodiments have not been described in detail so as not to unnecessarilyobscure the description. Furthermore, different embodiments aredescribed below. The embodiments may be used or performed together indifferent combinations.

The operation and effects of certain embodiments can be more fullyappreciated from a series of examples, as described below. Theembodiments on which these examples are based are representative only.The selection of those embodiments to illustrate the principles of theinvention does not indicate that materials, components, reactants,conditions, techniques, configurations and designs, etc. which are notdescribed in the examples are not suitable for use, or that subjectmatter not described in the examples is excluded from the scope of theappended claims and their equivalents. The significance of the examplescan be better understood by comparing the results obtained therefromwith potential results which can be obtained from tests or trials thatmay be or may have been designed to serve as controlled experiments andprovide a basis for comparison.

As used herein, the terms “based on”, “comprises”, “comprising”,“includes”, “including”, “has”, “having” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent). Also, use of the “a” or “an” is employed to describe elementsand components. This is done merely for convenience and to give ageneral sense of the description. This description should be read toinclude one or at least one and the singular also includes the pluralunless it is obvious that it is meant otherwise.

The meaning of abbreviations and certain terms used herein is asfollows: “Å” means angstrom(s), “g” means gram(s), “mg” meansmilligram(s), “μg” means microgram(s), “L” means liter(s), “mL” meansmilliliter(s), “cc” means cubic centimeter(s), “cc/g” means cubiccentimeters per gram, “mol” means mole(s), “mmol” means millimole(s),“M” means molar concentration, “wt. %” means percent by weight, “Hz”means hertz, “mS” means millisiemen(s), “mA” mean milliamp(s), “mAh/g”mean milliamp hour(s) per gram, “mAh/g S” mean milliamp hour(s) per gramsulfur based on the weight of sulfur atoms in a sulfur compound, “V”means volt(s), “x C” refers to a constant current that may fullycharge/discharge an electrode in 1/x hours, “SOC” means state of charge,“SEI” means solid electrolyte interface formed on the surface of anelectrode material, “kPa” means kilopascal(s), “rpm” means revolutionsper minute, “psi” means pounds per square inch, “maximum dischargecapacity” is the maximum milliamp hour(s) per gram of a positiveelectrode in a Li—S cell at the beginning of a discharge phase (i.e.,maximum charge capacity on discharge), “coulombic efficiency” is thefraction or percentage of the electrical charge stored in a rechargeablebattery by charging and is recoverable during discharging and isexpressed as 100 times the ratio of the charge capacity on discharge tothe charge capacity on charging, “pore volume” (i.e., Vp) is the sum ofthe volumes of all the pores in one gram of a substance and may beexpressed as cc/g, “porosity” (i.e., “void fraction”) is either thefraction (0-1) or the percentage (0-100%) expressed by the ratio:(volume of voids in a substance)/(total volume of the substance).

As used herein and unless otherwise stated the term “cathode” is used toidentify a positive electrode and “anode” to identify the negativeelectrode of a battery or cell. The term “battery” is used to denote acollection of one or more cells arranged to provide electrical energy.The cells of a battery can be arranged in various configurations (e.g.,series, parallel and combinations thereof).

The term “sulfur compound” as used herein refers to any compound thatincludes at least one sulfur atom, such as elemental sulfur and othersulfur compounds, such as lithiated sulfur compounds including disulfidecompounds and polysulfide compounds. For further details on examples ofsulfur compounds particularly suited for lithium batteries, reference ismade to “A New Entergy Storage Material: Organosulfur Compounds Based onMultiple Sulfur-Sulfur Bonds”, by Naoi et al., J. Electrochem. Soc.,Vol. 144, No. 6, pp. L170-L172 (June 1997), which is incorporated hereinby reference in its entirety.

The term “ionomer”, as used herein, refers to any polymer including anionized functional group (e.g., sulfonic acid, phosphonic acid,phosphoric acid or carboxylic acid, such as acrylic or methacrylic acid(i.e., “(meth)acrylic acid”) in which the acid group is neutralized witha base including an alkali metal, such as lithium, to form an ionizedfunctionality, such as lithium methacrylate). An ionomer may be made byvarious methods including polymerizing ionic monomers and by chemicallymodifying ionogenic polymers. The term “hydrocarbon ionomer”, as usedherein, refers to any ionomer not including any halogen atomsincorporated by a covalent bond into a site (e.g., the polymer backboneor branching) on the ionomer.

According to the principles of the invention, as demonstrated in thefollowing examples and embodiments, there are Li—S cells incorporatinghydrocarbon ionomer articles, such as coatings, films, and membranes.The hydrocarbon ionomer articles may be associated with various elementsin a Li—S cell, such as a hydrocarbon ionomer coating on a porousseparator or an interior wall of the cell. According to variousembodiments, different types of hydrocarbon ionomers may be used informing one or more of the articles in a cell, such as an ionomercontaining acrylate groups based on ionized acrylic acid, methacrylategroups based on ionized methacrylic acid or a combination of bothacrylate and methacrylate (i.e., (meth)acrylate) groups.

Examples of hydrocarbon ionomers include SURLYN® and derivatives ofSURLYN®, a copolymer of ethylene and (meth)acrylic acid. Depending uponthe commercially available grade of SURLYN® that is used, an amount ofthe ionizable (meth)acrylic acid groups in the SURLYN® can beneutralized to their ionic (meth)acrylate salt. Other examples ofhydrocarbon ionomers include sulfonated polyacrylamide and sulfonatedpolystyrene. Other hydrocarbon ionomers may also be utilized, such asionomers having ionomer functional groups based on neutralizedcarboxylic acids, phosphonic acids, phosphoric acids and/or otherionomer functional groups.

Different types of copolymers may be hydrocarbon ionomers, such ascopolymers with different non-ionic monomers or multiple types of ionicmonomers. Other hydrocarbon ionomers may also be utilized or combined ina hydrocarbon ionomer article, such as different hydrocarbon ionomerswith different structures and/or different substituents which may be thesame or different ionomer functional groups. As noted above, hydrocarbonionomers never contain halogen or halogen-containing substituents, butmay include other substituents. In an embodiment, a hydrocarbon ionomermay include alcohol and alkyl substituents. For example, a hydrocarbonionomer may include unsaturated branches with or without any functionalgroups or substituents. The substituent sites on a hydrocarbon ionomermay be located anywhere in the polymer, such as along the backbone andalong any branching which may be present.

Hydrocarbon ionomer may be combined with other components to formhydrocarbon ionomer articles which can be incorporated into a Li—S cell,according to various embodiments. The hydrocarbon ionomer may beidentified or quantified with respect to other components in differentways within the article. For example, in a hydrocarbon ionomer articlewhich is a coated porous separator, the separator itself may be madefrom polyimide, such as a mat or other article made from polyimidefiber, or a polyethylene/polypropylene laminate which is then coatedwith a hydrocarbon ionomer. In another variant, a hydrocarbon ionomercomposition may be prepared which is a blend, such as a combinationincluding hydrocarbon ionomer and a modified polyethylene which ismodified to enhance its miscibility with the hydrocarbon ionomer.Additives may also be included, such as a polymer compatibilizer that iscombined with the components to stabilize the blend includinghydrocarbon ionomer. A composition comprising hydrocarbon ionomer may bemolded or press-formed to produce a hydrocarbon ionomer article, such asa porous separator, constituted by the hydrocarbon ionomer alone or ablend containing hydrocarbon ionomer. Hydrocarbon ionomer may also bepresent as a function of a structure associated with these embodiments,such as a weight measure of hydrocarbon ionomer per surface area of anarticle, such as a porous separator, or as a weight percentage of theporous separator constituted by a hydrocarbon ionomer blend.

An amount of hydrocarbon ionomer in an article may be quantified interms of an amount of hydrocarbon ionomer associated with a volume ofmaterial in a coating or a membrane, or below an area on the surface ofan element in an Li—S cell, such as a porous separator, an interior wallof the cell, a positive electrode, a negative electrode, a circuitcoupling electrodes or another cell element exposed to electrolytemedium in the cell. According to an embodiment, a suitable amount ofhydrocarbon ionomer in a coating is about 0.0001 to 100 mg/cm². In otherembodiments, a suitable amount of hydrocarbon ionomer in a coating isabout 0.001 to 75 mg/cm², about 0.001 to 50 mg/cm², about 0.001 to 35mg/cm², about 0.01 to 20 mg/cm², about 0.01 to 15 mg/cm², about 0.1 to10 mg/cm² and about 0.3 to 5 mg/cm².

An amount of hydrocarbon ionomer may be expressed as a weight percentagepresent in an article, such a membrane or a film. In this example, themembrane or film may be an element in another article, such as porousseparator. The hydrocarbon ionomer may also be part of more than onearticle, such as a porous separator made from a hydrocarbon ionomerblend and coated with a pure hydrocarbon ionomer coating. Thehydrocarbon ionomer loading in an element may be varied as desired.According to an embodiment, a suitable amount of hydrocarbon ionomer inan article is about 0.0001 to 100 wt. %. According to other embodiments,a suitable amount of hydrocarbon ionomer in an article is about 0.0001wt. % to about 99 wt. %, 98 wt. %, 95 wt. %, 90 wt. %, 85 wt. %, 80 wt.%, 75 wt. %, 70 wt. %, 65 wt. %, 60 wt. %, 55 wt. %, 50 wt. %, 45 wt. %,40 wt. %, 35 wt. %, 30 wt. %, 25 wt. %, 20 wt. %, 15 wt. %, 10 wt. %, 5wt. %, 2 wt. %, 1 wt. %, 0.1 wt. %, 0.01 wt. % and 0.001 wt. %.

In an embodiment, a hydrocarbon ionomer article may modify anotherelement in a cell, such as a hydrocarbon ionomer coating on a porousseparator. In another embodiment, a hydrocarbon ionomer article may forma separate element in a cell, such as a hydrocarbon ionomer film or amembrane which is situated in the cell solution, separate from otherelements in the cell. Such an article may float freely in the cellsolution or be secured, such as affixed to a cell wall. In thiscircumstance, the hydrocarbon ionomer film or membrane, may be fully orpartially situated within the electrolyte medium, such as a cellsolution in a Li—S cell, and may be secured by fastening an edge of thefilm or membrane to the interior wall of the cell or affixing it toanother element or part in the cell.

Referring to FIG. 1, depicted is a cell 100, such as a Li—S cell in aLi—S battery. Cell 100 includes a lithium containing negative electrode101, a sulfur-containing positive electrode 102, a circuit 106 and aporous separator 105. A cell container wall 107 contains the elements inthe cell 100 with an electrolyte medium, such as a cell solutioncomprising solvent and electrolyte. The positive electrode 102 includesa circuit contact 104. The circuit contact 104 provides a conductiveconduit through a metallic circuit 106 coupling the negative electrode101 and the positive electrode 102. The positive electrode 102 isoperable in conjunction with the negative electrode 101 in the cell 100to store electrochemical voltaic energy and release electrochemicalvoltaic energy, this converting chemical and electrical energy from oneform to the other, depending upon the whether the cell 100 is in thecharge phase or discharge phase. A porous carbon material, such as acarbon powder, having a high surface area and a high pore volume, may beutilized in the making the positive electrode 102. According to anembodiment, sulfur compound, such as elemental sulfur, lithium sulfide,and combinations of such, may be introduced to the porous regions withinthe carbon powder to make a carbon-sulfur (C—S) composite which isincorporated into a cathode composition in the positive electrode 102. Apolymeric binder may also be incorporated into the cathode compositionwith the C—S composite in the positive electrode 102. In addition, othermaterials may be utilized in the positive electrode 102 to host thesulfur compound as an alternative to the carbon powder, such asgraphite, graphene and carbon fibers. The construction of the positiveelectrode 102 may be varied as desired.

The porous separator 105 in cell 100 incorporates a composition 103, andis a hydrocarbon ionomer article. The composition 103 compriseshydrocarbon ionomer, optionally in a blend including other componentssuch as additives and/or other polymers which are miscible with thehydrocarbon ionomer. An example of such a miscible polymer is anethylene copolymer with polar functional groups grafted to promotemiscibility with the hydrocarbon ionomer in the composition 103. Whensituated in the cell 100, the composition 103 within the porousseparator 105 may be exposed to an amount of the cell solution containedinside or passing through a pore volume within the porous separator 105.The exposed areas of the composition 103 within the porous separator 105appears to function as a barrier to limit the passage of soluble sulfurcompounds “shuttling” through the cell solution within the pore volumefrom reaching the negative electrode 101. The composition 103 may alsofunction as a reservoir through adsorption of the sulfur compounds fromthe cell solution in the pore volume, thus withdrawing these sulfurcompounds temporarily from the cell solution in the pore volume of theporous separator 105. However, the composition 103 in the porousseparator 105 still permits diffusion of lithium ions through the porevolume to and from the negative electrode 101 during charge anddischarge phases in the cell 100.

Cell 100 also includes membranes 111, 112 and 115, coatings 113 and 114and films 110 and 116, all of which are hydrocarbon ionomer articles.These elements of cell 100 incorporate compositions comprisinghydrocarbon ionomer. The compositions may be the same or different fromeach other and composition 103.

Membrane 111 is an anodic-membrane as it is affixed or in closeproximity to a surface of the negative electrode 101. Membrane 111comprises hydrocarbon ionomer. In an embodiment, membrane 111 includes aprotective layer, separating lithium metal in the negative electrode 101from the hydrocarbon ionomer in membrane 111. The protective layercomprises a permeable substance which is substantially inert to lithiummetal in the negative electrode 101. Suitable inert substances includeporous films containing polypropylene and polyethylene. According to anembodiment, the hydrocarbon ionomer in membrane 111 is a derivative ofSURLYN® in which the SURLYN® is partially neutralized with a lithium ionsource. In other embodiments, membrane 111 may comprise otherhydrocarbon ionomers, as alternatives or in addition to the SURLYN®derivative in the anodic-membrane. The membrane 111 is permeable, butfunctions in the cell 100 as a barrier to limit the passage of solublesulfur compounds in the cell solution from reaching the negativeelectrode 101. Membrane 111 may also function as a reservoir throughadsorption of soluble sulfur compounds from the cell solution or byotherwise limiting their passage through a pore structure in themembrane 111. However, membrane 111 permits diffusion of lithium ions toand from the negative electrode 101 during charge-discharge cycles inthe cell 100.

Coatings 113 and 114 are applied to respective separate surfaces of theporous separator 105. The coatings 113 and 114 may be applied throughvarious well-known techniques such as spray coating, dip coating and thelike. Coatings 113 and 114 comprise hydrocarbon ionomer, such as ahydrocarbon ionomer with carboxylate, sulfonate, phosphate, and/orphosphonate groups, or may comprise a plurality of different types ofhydrocarbon ionomer. Like the membrane 111, the coatings 113 and 114 arepermeable, but appear to function as a barrier to soluble sulfurcompounds from reaching the negative electrode 101 by limiting theirpassage by diffusion through the cell solution. The coatings 113 and 114may also function as reservoirs for the sulfur compounds, possiblythrough adsorption or by otherwise limiting the passage of solublesulfur compounds through pores in coatings 113 and 114. While thecoatings 113 and 114 appear to act as barriers and/or reservoirs forsoluble sulfur compounds in the cell solution, they permit the diffusionof lithium ions to and from the negative electrode 101 duringcharge-discharge cycles in the cell 100.

Membranes 112 and 115 are fully situated within the cell solution of thecell 100. Both membranes 112 and 115 are located between positiveelectrode 102 and the negative electrode 101. However, the respectivemembranes are on different respective sides of the porous separator 105.Membranes 112 and 115 may be secured within cell 100 by being affixed toanother object in the cell 100, such as the cell container wall 107.Membranes 112 and 115 comprise hydrocarbon ionomer with ionic functionalgroups, such as carboxylate, sulfonate, phosphate and/or phosphonategroups and may comprise a plurality of different types of hydrocarbonionomer. Membranes 112 and 115 are permeable, but they function to limitthe passage of soluble sulfur compounds in the cell solution fromreaching the negative electrode 101 by acting as barriers to the sulfurcompounds. Membranes 112 and 115 may also act as reservoirs throughadsorption of the sulfur compounds. However, the membranes 112 and 115permit the diffusion of lithium ions through their respective pores topass between the positive electrode 102 and the negative electrode 101during charge-discharge cycles in the cell 100.

Films 110 and 116 are situated in the cell 100 so as to be partiallyexposed to the cell solution. Films 110 and 116 do not separate thepositive electrode 102 and negative electrode 101. Therefore, films 110and 116 may be permeable or impermeable. Films 110 and 116 are securedwithin cell 100 by being affixed to the cell container wall 107. Therespective films 110 and 116 comprise respective hydrocarbon ionomerthat may be the same or different, such as a hydrocarbon ionomer withcarboxylate, sulfonate, phosphate, and/or phosphonate groups and maycomprise a plurality of different types of hydrocarbon ionomer. Althoughthe films 110 and 116 may not be permeable, they appear to function asreservoirs to soluble sulfur compounds, and limit the passage of sulfurcompounds in the cell solution from reaching the negative electrode 101.Without being bound by any particular theory, they appear to accomplishthis through the adsorption of sulfur compounds from the electrolytesolution during charge-discharge cycles in the cell 100.

According to the principles of the invention, a Li—S cell, such as cell100, incorporates at least one hydrocarbon ionomer article and mayincorporate multiple hydrocarbon ionomer articles as demonstrated incell 100, and in various other combinations and configurations. In oneembodiment, the hydrocarbon ionomer articles comprise a polymericsulfonate. In another embodiment, the hydrocarbon ionomer articlescomprise a polymeric carboxylate. In yet another embodiment thehydrocarbon ionomer articles comprise a polymeric phosphate. In yetanother embodiment the hydrocarbon ionomer articles comprise a polymericphosphonate. In still another embodiment, the hydrocarbon ionomerarticles comprise a copolymer including at least two types of ionicfunctionality. In still yet another embodiment, the hydrocarbon ionomerarticles comprise at least two different types of hydrocarbon ionomerwith different ionic functionality in the different types of hydrocarbonionomers.

Hydrocarbon ionomers which are suitable for use herein, include ionomerswhich include pendant negatively charged functional groups which areneutralized. The negatively charged functional groups, such as an acid(e.g., carboxylic acid, phosphonic acid and sulfonic acid) or an amide(e.g., acrylamide). These negatively charged functional groups areneutralized, fully or partially with a metal ion, preferably with analkali metal. Lithium is preferred for utilization in a Li—S cell. Thehydrocarbon ionomers may contain negatively-charged functional groups,exclusively (i.e., anionomers) or may contain a combination ofnegatively-charged functional groups with some positively-chargedfunctional groups (i.e., ampholytes).

The hydrocarbon ionomers may include ionic monomer units copolymerizedwith nonionic (i.e., electrically neutral) monomer units. Thehydrocarbon ionomers can be prepared by polymerization of ionicmonomers, such as ethylenically unsaturated carboxylic acid comonomers.Other hydrocarbon ionomers which are suitable for making the articlesare ionically modified “ionogenic” polymers which made ionomers bychemical modification of negatively charged functional groups on theionogenic polymer (i.e., chemical modification after polymerization),such as by treatment of a polymer having carboxylic acid functionalitywhich is chemically modified by neutralizing to form ester-containingcarboxylate functional groups which are ionized with an alkali metal,thus forming negatively charged ionic functionality. The ionicfunctional groups may be randomly distributed or regularly located inthe hydrocarbon ionomers.

The hydrocarbon ionomers may be polymers including ionic and non-ionicmonomeric units in a saturated or unsaturated backbone, optionallyincluding branching, which is carbon based and may include otherelements, such as oxygen or silicon. The negatively charged functionalgroups may be any species capable of forming an ion with an alkalimetal. These include, but are not limited to, sulfonic acids, carboxylicacids and phosphonic acids. According to an embodiment, the polymerbackbone or branches in the hydrocarbon ionomer may include comonomerssuch as alkyls. Alkyls which are α-olefins are preferred. Suitableα-olefin comonomers include, but are not limited to, ethylene,propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 3 methyl-1-butene,4-methyl-1-pentene, styrene and the like and mixtures of two or more ofthese α-olefins.

According to an embodiment, hydrocarbon ionomers are ionogenic acidcopolymers which are neutralized with a base so that the acid groups inthe precursor acid copolymer form ester salts, such as carboxylate orsulfonate groups. The precursor acid copolymer groups may be fullyneutralized or partially neutralized to a “neutralization ratio” basedon the amount neutralized of all the negatively charged functionalgroups that may be neutralized in the ionomer. According to anembodiment, the neutralization ratio is 0% to about 1%. In otherembodiments, the neutralization ratio is about 5%, about 10%, about 20%,about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about90%, about 95%, or about 100%. According to an embodiment, theneutralization ratio is about 0% to 90%. In other embodiments, theneutralization ratio is about 20% to 80%, about 30% to 70%, about 40% to60% or about 50%.

The neutralization ratio may be selected for different properties, suchas to promote conductivity in the ionomer, to promote the dispersabilityof the hydrocarbon ionomer in a particular solvent or to promotemiscibility with another polymer in a blend. Methods of changing theneutralization ratio include increasing the neutralization, such as byintroducing basic ion sources to promote a greater degree of ionizationamong the monomer units. Methods of changing the neutralization ratioalso include those for decreasing neutralization, such as by introducinga highly neutralized ionomer to strong acids so as to convert some orall of an ionic functionality (e.g., (meth)acrylate) to an acid (e.g.,(meth)acrylic acid).

Although any stable cation is believed to be suitable as a counter-ionto the negatively charged functional groups in a hydrocarbon ionomer,monovalent cations, such as cations of alkali metals, are preferred.Still more preferably, the base is a lithium ion-containing base, toprovide a lithiated hydrocarbon ionomer wherein part or all of theprecursor groups are replaced by lithium salts. To obtain thehydrocarbon ionomers, the precursor polymers may be neutralized by anyconventional procedure with an ion source. Typical ion sources includesodium hydroxide, sodium carbonate, zinc oxide, zinc acetate, magnesiumhydroxide, and lithium hydroxide. Other ion sources are well known and alithium ion source is preferred.

According to an embodiment, a a suitable hydrocarbon ionomer includesethylene-(meth)acrylic acid copolymer having about 5 to 25 wt. %(meth)acrylic acid monomer units based on the weight of theethylene-(meth)acrylic acid copolymer; and more particularly, theethylene-(meth)acrylic acid copolymer has a neutralization ratio of 0.40to about 0.70. Hydrocarbon ionomers suitable for use herein areavailable from various commercial sources or they can be prepared bysynthesis.

SURLYN® is an example of a carboxylate hydrocarbon ionomer which is arandom copolymer-poly(ethylene-co-(meth)acrylic acid). E.I. du Pont deNemours and Co., Wilmington, Del., provides the SURLYN® resin brand, acopolymer of ethylene and (meth)acrylic acid. It is produced through thecopolymerization of ethylene and (meth)acrylic acid via a high pressurefree radical reaction, similar to that for the production of low densitypolyethylene and has an incorporation ratio of (meth)acrylic comonomerthat is relatively low and is typically less than 20% per mole and oftenless than 15% per mole of the copolymer. Variants of the SURLYN® resinbrand are disclosed in U.S. Pat. No. 6,518,365 which is incorporated byreference herein in its entirety. According to an embodiment,particularly useful hydrocarbon ionomers include SURLYN® and variants ofSURLYN® which are derivatives of commercially available forms ofSURLYN®. One SURLYN® variant may be made by treating SURLYN® with astrong acid to reduce the overall neutralization ratio to promote itsdispersability in aqueous solution. According to another variant,SURLYN® is ion-exchanged to increase the lithium ion content.

The hydrocarbon ionomer may be neutralized. Neutralization of thehydrocarbon ionomer may be with a neutralization agent that may berepresented by the formulas MA where M is a metal ion and A is theco-agent moiety such as an acid or base. Metal ions suitable as themetal ion include monovalent, divalent, trivalent and tetravalentmetals. Metal ions suitable for use herein include, but are not limitedto, ions of Groups IA, IB, IIA, IIB, IIIA, IVA, IVB, VB, VIIB, VIIB andVIII metals of the Periodic Table. Examples of such metals include Na⁺,Li⁺, K⁺ and Sn⁴⁺. Li⁺ is preferred for uses of the hydrocarbon ionomerin a Li—S cell.

Neutralization agents suitable for use herein include any metal moietywhich would be sufficiently basic to form a salt with a low molecularweight organic acid, such as benzoic acid or p-toluene sulfonic acid.One suitable neutralization agent is lithium hydroxide distributed bySigma Aldrich (Sigma Aldrich, 545856). Other neutralization agents andneutralization processes to form hydrocarbon ionomers are described inU.S. Pat. No. 5,003,012 which is incorporated by reference herein in itsentirety.

Other hydrocarbon ionomers which are suitable include block copolymerssuch as those derived from the sulphonation ofpolystyrene-b-polybutadiene-b-polystyrene. Sulfonated polysulphones andsulfonated polyether ether ketones are also suitable. Phosphonatehydrocarbon ionomers may also be used, as well as copolymers with morethan one ionic functionality. For example, direct co-polymerization ofdibutyl vinylphosphonate with acrylic acid yields a mixedcarboxylate-phosphonate ionomer. Copolymers derived from vinylphosphonates with styrene, methyl methacrylate, and acrylamide may alsobe used. Phosphorus containing polymers can also be made afterpolymerization by phosphonylation reactions, typically with POCl₃. Forexample, phosphonylation of polyethylene can produce apolyethylene-phosphonic acid copolymer.

Hydrocarbon ionomers which are suitable for use include carboxylate,sulfonate and phosphonate hydrocarbon ionomers. Others are alsosuitable, such as styrene alkoxide hydrocarbon ionomers such as thosederived from polystyrene-co-4-methoxy styrene. A hydrocarbon ionomer mayhave a polyvinyl or a polydiene backbone. Different hydrocarbon ionomersmay differ in properties, partly due to differences in the strength ofthe ionic interactions and structure. Carboxylate hydrocarbon ionomers,sulfonate hydrocarbon ionomers, and their mixtures are preferred. Alsohydrocarbon ionomers in which the negatively charged ionic functionalgroups are neutralized with a lithium ion source to form a salt withlithium are preferred.

The positive electrode 102 in cell 100 may be made by incorporating acathode composition comprising carbon-sulfur (C—S) composite made fromsulfur compound and carbon powder. The cathode composition may alsoinclude a non-ionomeric polymeric binder, a carbon black and ahydrocarbon ionomer.

A representative carbon powder for making the C—S composite isKETJENBLACK EC-600JD, distributed by Akzo Nobel having an approximatesurface area of 1400 m²/g BET (Product Data Sheet for KETJENBLACKEC-600JD, Akzo Nobel) and an approximate pore volume of 4.07 cc/gram, asdetermined according to the BJH method, based on a cumulative porevolume for pores ranging from 17-3000 angstroms. In the BJH method,nitrogen adsorption/desorption measurements were performed on ASAP model2400/2405 porosimeters (Micrometrics, Inc., No. 30093-1877). Sampleswere degassed at 150° C. overnight prior to data collection. Surfacearea measurements utilized a five-point adsorption isotherm collectedover 0.05 to 0.20 p/p₀ and were analyzed via the BET method, describedin Brunauer et al., J. Amer. Chem. Soc., v. 60, no. 309 (1938), andincorporated by reference herein in its entirety. Pore volumedistributions utilized a 27 point desorption isotherm and were analyzedvia the BJH method, described in Barret, et al., J. Amer. Chem. Soc., v.73, no. 373 (1951), and incorporated by reference herein in itsentirety.

Additional commercially available carbon powders which may be utilizedinclude KETJEN 300: approximate pore volume 1.08 cc/g (Akzo Nobel) CABOTBLACK PEARLS: approximate pore volume 2.55 cc/g, (Cabot), PRINTEX XE-2B:approximate pore volume 2.08 cc/g (Orion Carbon Blacks, The CaryCompany). Other sources of such carbon powders are known to those havingordinary skill in the art.

Other porous carbon materials suitable for use herein may bemanufactured or synthesized using known processes, as desired, for theirpore volume, surface area and other features. Porous carbon materialssuitable for use herein include templated carbons. Templated carbon hasa synthesized carbon microstructure which is complementary to aninorganic template used in making the templated carbon. Templated carbonmaterials are demonstrated in co-assigned and co-pending U.S. PatentApplication Ser. No. 61/587,805, filed on Jan. 18, 2013, based onAttorney Docket No.: CL-5409, which is incorporated by reference hereinin its entirety.

Carbon powders which are suitable for making the C—S composite includethose having a surface area of about 100 to 4,000 square meters per gramcarbon powder, about 200 to 3,000 square meters per gram, about 300 to2,500 square meters per gram carbon powder, about 500 to 2,200 squaremeters per gram, about 700 to 2,000 square meters per gram, about 900 to1,900 square meters per gram, about 1,100 to 1,700 square meters pergram and about 1,300 to 1,500 square meters per gram carbon powder.

Carbon powders which are suitable for making the C—S composite alsoinclude those having a pore volume ranging from about 0.25 to 10 cc pergram carbon powder, from about 0.7 to 7 cc per gram, from about 0.8 to 6cc per gram, from about 0.9 to 5.5 cc per gram, from about 1 to 5.2 ccper gram, from about 1.1 to 5.1 cc per gram, from about 1.2 to 5 cc pergram, from about 1.4 to 4 cc per gram, and from about 2 to 3 cc pergram. A particularly useful carbon powder is one having a pore volumethat is greater than 1.2 cc per gram and less than 5 cc per gram carbonpowder.

Sulfur compounds which are suitable for making the C—S composite includemolecular sulfur in its various allotropic forms and combinationsthereof, such as “elemental sulfur”. Elemental sulfur is a common namefor a combination of sulfur allotropes including puckered S₈ rings, andoften including smaller puckered rings of sulfur. Other sulfur compoundswhich are suitable are compounds containing sulfur and one or more otherelements. These include lithiated sulfur compounds, such as for example,Li₂S or Li₂S₂. A representative sulfur compound is elemental sulfurdistributed by Sigma Aldrich as “Sulfur”, (Sigma Aldrich, 84683). Othersources of such sulfur compounds are known to those having ordinaryskill in the art.

A non-ionomer polymeric binder which may be utilized for making thecathode composition includes polymers exhibiting chemical resistance,heat resistance as well as binding properties, such as polymers based onalkylenes, oxides and/or fluoropolymers. Examples of these polymersinclude polyethylene oxide (PEO), polyisobutylene (PIB), andpolyvinylidene fluoride (PVDF). A representative polymeric binder ispolyethylene oxide (PEO) with an average M_(w) of 600,000 distributed bySigma Aldrich as “Poly(ethylene oxide)”, (Sigma Aldrich, 182028).Another representative polymeric binder is polyisobutylene (PIB) with anaverage M_(w) of 4,200,000 distributed by Sigma Aldrich as“Poly(isobutylene)”, (Sigma Aldrich, 181498). Polymeric binders whichare suitable for use herein are also described in U.S. Published PatentApplication No. US2010/0068622, which is incorporated by referenceherein in its entirety. Other sources of polymeric binders are known tothose having ordinary skill in the art.

Carbon blacks which are suitable for making the cathode compositioninclude carbon substances exhibiting electrical conductivity andgenerally having a lower surface area and lower pore volume relative tothe carbon powder described above. Carbon blacks typically are colloidalparticles of elemental carbon produced through incomplete combustion orthermal decomposition of gaseous or liquid hydrocarbons under controlledconditions. Other conductive carbons which are also suitable are basedon graphite. Suitable carbon blacks include acetylene carbon blackswhich are preferred. A representative carbon black is SUPER C65distributed by Timcal Ltd. and having BET nitrogen surface area of 62m²/g carbon black measured by ASTM D3037-89. Other commercial sources ofcarbon black, and methods of manufacturing or synthesizing them, areknown to those having ordinary skill in the art.

Carbon blacks which are suitable for use herein include those having asurface area ranging from about 10 to 250 square meters per gram carbonblack, about 30 to 200 square meters per gram, about 40 to 150 squaremeters per gram, about 50 to 100 square meters per gram and about 60 to80 square meters per gram carbon black.

The C—S composite includes a porous carbon material, such as carbonpowder, containing the sulfur compound situated in the carbonmicrostructure of the porous carbon material. The amount of sulfurcompound which may be contained in the C—S composite (i.e., the sulfurloading in terms of the weight percentage of sulfur compound, based onthe total weight of the C—S composite, is dependent to an extent on thepore volume of the carbon powder. Accordingly, as the pore volume of thecarbon powder increases, higher sulfur loading with more sulfur compoundis possible. Thus, a sulfur compound loading of, for example, about 5wt. %, 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40wt. %, 45 wt. %, 50 wt. %, 55 wt. %, 60 wt. %, 65 wt. %, 70 wt. %, 75wt. %, 80 wt. %, 85 wt. %, 85 wt. %, 90 wt. % or 95 wt. % may be used.Ranges among these amounts define embodiments which may be used.

The cathode composition may include various weight percentages of C—Scomposite. The cathode composition may optionally include non-ionomerpolymeric binder, hydrocarbon ionomer, and carbon black in addition tothe C—S composite. Exclusive of the amount of hydrocarbon ionomerpresent, C—S composite is generally present in the cathode compositionin an amount which is greater than 50 wt. % of the remainder (i.e.,excluding hydrocarbon ionomer) of the cathode composition. Higherloading with more C—S composite is possible. Thus, exclusive of theamount of hydrocarbon ionomer present, a C—S composite loading of, forexample, about 55 wt. %, 60 wt. %, 65 wt. %, 70 wt. %, 75 wt. %, 80 wt.%, 85 wt. %, 90 wt. %, 95 wt. %, 98 wt. %, or 99 wt. % may be used.According to an embodiment, exclusive of the amount of hydrocarbonionomer present, about 50 to 99 wt. % C—S composite may be used. Inanother embodiment, exclusive of the amount of hydrocarbon ionomerpresent, about 70 to 95 wt. % C—S composite may be used. Ranges amongthese amounts define embodiments which may be used.

Exclusive of the amount of hydrocarbon ionomer present, polymeric binder(i.e., non-ionomer polymeric binder) may be present in the cathodecomposition in an amount which is greater than 1 wt. %. Higher loadingwith more polymeric binder is possible. Thus, a polymeric binder loadingof, for example, about 2 wt. %, 3 wt. %, 4 wt. %, 5 wt. %, 6 wt. %, 7wt. %, 8 wt. %, 9 wt. %, 10 wt. %, 12 wt. %, 14 wt. %, 16 wt. %, or 17.5wt. % may be used exclusive of the amount of hydrocarbon ionomerpresent. According to an embodiment, about 1 to 17.5 wt. % polymericbinder may be used exclusive of the amount of hydrocarbon ionomerpresent. In another embodiment, about 1 to 12 wt. % polymeric binder maybe used exclusive of the amount of hydrocarbon ionomer present. Inanother embodiment, about 1 to 9 wt. % polymeric binder may be usedexclusive of the amount of hydrocarbon ionomer present. Ranges amongthese amounts define embodiments which may be used.

According to an embodiment, the carbon black may optionally be presentin the cathode composition in an amount which is greater than 0.01 wt.%. Higher loading with more carbon black is possible. Thus, a carbonblack loading, exclusive of the amount of hydrocarbon ionomer present,of about 0.1 wt. %, about 1 wt. %, about 2 wt. %, 3 wt. %, 4 wt. %, 5wt. %, 6 wt. %, 8 wt. %, 10 wt. %, 12 wt. %, 14 wt. %, 15 wt. %, or 20wt. % may be used. According to an embodiment, about 0.01 to 15 wt. %carbon black may be used, exclusive of the amount of hydrocarbon ionomerpresent. In another embodiment, about 5 to 10 wt. % carbon black may beused, exclusive of the amount of hydrocarbon ionomer present. Rangesamong these amounts define embodiments which may be used.

The C—S composite may made by various methods, including simply mixing,such as by dry grinding, the carbon powder with the sulfur compound. C—Scomposite may also be made by introducing the sulfur compound into themicrostructure of the carbon powder utilizing such vehicles as heat,pressure, liquid (e.g., a dissolution of sulfur compound in carbondisulfide and impregnation by contacting the solution with the carbonpowder), etc.

Useful methods for introducing sulfur compound into the carbon powderinclude melt imbibement and vapor imbibement. These are compositingprocesses for introducing the sulfur compound into the microstructure ofthe carbon powder utilizing such vehicles as heat, pressure, liquid,etc.

In melt imbibement, a sulfur compound, such as elemental sulfur can beheated above its melting point (about 113° C.) while in contact with thecarbon powder to impregnate it. The impregnation may be accomplishedthrough a direct process, such as a melt imbibement of elemental sulfur,at a raised temperature, by contacting the sulfur compound and carbon ata temperature above 100° C., such as 160° C. A useful temperature rangeis 120° C. to 170° C.

Another imbibement process which may be used for making the C—Scomposite is vapor imbibement which involves the deposition of sulfurvapor. The sulfur compound may be raised to a temperature above 200° C.,such as 300° C. At this temperature, the sulfur compound is vaporizedand placed in proximity to, but not necessarily in direct contact with,the carbon powder.

These processes may be combined. For example, melt imbibement processcan be followed by a higher temperature process. Alternatively, thesulfur compound can be dissolved in carbon disulfide to form a solutionand the C—S composite can be formed by contacting this solution with thecarbon powder. The C—S composite is prepared by dissolving sulfurcompound in non-polar solvent such as toluene or carbon disulfide andcontacted with the carbon powder. The solution or dispersion can becontacted, optionally, at incipient wetness to promote an evendeposition of the sulfide compound into the pores of the carbon powder.Incipient wetness is a process in which the total liquid volume exposedto the carbon powder does not exceed the volume of the pores of thatporous carbon material. The contacting process can involve sequentialcontacting and drying steps to increase the weight % loading of thesulfur compound.

Sulfur compound may also be introduced to the carbon powder by othermethods. For example, sodium sulfide (Na₂S) can be dissolved in anaqueous solution to form sodium polysulfide. The sodium polysulfide canbe acidified to precipitate the sulfur compound in the carbon powder. Inthis process, the C—S composite may require thorough washing to removesalt byproducts.

Suitable introducing methods include melt imbibement and vaporimbibement. One method of melt imbibement includes heating elementalsulfur (Li₂S will not melt under these conditions) and carbon powder atabout 120° C. to about 170° C. in an inert gas, such as nitrogen. Avapor imbibement method may also be utilized. In the vapor imbibementmethod, sulfur vapor may be generated by heating a sulfur compound, suchas elemental sulfur, to between the temperatures of about 120° C. and400° C. for a period of time, such as about 6 to 72 hours in thepresence of the carbon powder. Other examples of melt imbibement andvapor imbibement are shown in co-assigned and co-pending U.S. PatentApplication Ser. No. 61/587,805, filed on Jan. 18, 2013, based onAttorney Docket No.: CL-5409, which is incorporated by reference above.

According to an embodiment, a C—S composite formed by a compositingprocess may be combined with hydrocarbon ionomer and, optionally,polymeric binder and carbon black by conventional mixing or grindingprocesses. A solvent, preferably an organic solvent, such as toluene,alcohol, or n-methylpyrrolidone (NMP) may optionally be utilized. Thesolvent should preferably not react with the hydrocarbon ionomer orpolymeric binder, if any, so as to break these down, or significantlyalter them. Conventional mixing and grinding processes are known tothose having ordinary skill in the art. The ground or mixed componentsmay form a composition 103, according to an embodiment, which may beprocessed or incorporated and/or formed into an electrode.

According to another embodiment, a layering or an electrodeincorporating a cathode composition may be made through a layeringprocess to form the layering and the electrode. The layering process mayutilize, for example, a porous carbon material, such as carbon powder,having a pore volume greater than 1.2 cc/g in a C—S composite. Thelayering and the electrode may be formed through the application of oneor several individual layers on a surface of a detachable substrate. Thehydrocarbon ionomer may be incorporated into the layering in a varietyof ways, including simply mixing the hydrocarbon ionomer in acomposition with the C—S composite and optionally, a polymeric binderand any other components.

The hydrocarbon ionomer may also be incorporated by applying separatecoats including a hydrocarbon ionomer in a composition with a lesseramount or excluding the C—S composite and/or other components such aspolymeric binder and carbon black. In one example, after a compositionincluding the C—S composite is applied to form a layering/electrode, thehydrocarbon ionomer may be applied in a separate layer above the basecomposition with the C—S composite. In another example, the hydrocarbonionomer may be applied as a dispersion which is interleaved or appliedin alternate coating applications along with a base compositionincluding C—S composite.

The individual layers in a spray coated layering or electrode may havethe same or different proportions of different components. For example,different sets of materials with different components and differentproportions of components may be prepared and applied in combination toform a layering or electrode. One or more components may be completelyabsent from any one material applied this way. The different materialsmay be applied using different coating apparatuses and differentapplication techniques.

For example, two cathode compositions with different C—S components maybe prepared with different C—S composites or different amounts of C—Scomposites. In this example, the respective C—S composites in the twodifferent C—S components may have respective porous carbon materialswith differing physical properties, respective sulfur loadings, etc. Thetwo cathode compositions may be applied in alternate passes of spraycoating for a layering in an electrode with an average amount of the twocompositions throughout or with localized concentrations of one or theother of the two compositions. The components in the different sets ofcompositions may vary according to multiple parameters, such asrespective hydrocarbon ionomers, respective weight percentageshydrocarbon ionomer, respective polymeric binders, respective weightpercentages polymeric binder, respective C—S composites, respectiveweight percentages C—S composite, respective carbon powders andrespective weight percentages sulfur in the respective C—S composites ofthe different compositions.

Also, a porogen (i.e., a void or pore generator) may be included withinthe layers themselves in the positive electrode. A porogen is anyadditive which can be removed by a chemical or thermal process to leavebehind a void, changing the pore structure of the layering or electrode.This level of porosity control may be utilized in terms of managing masstransfer in a laying or electrode layer. For example, a porogen may be acarbonate, such as calcium carbonate powder, which is added to an inkslurry and then coated in combination with other components in the inkslurry, such as C—S composite, polymeric binder and an optionalconductive carbon, onto an aluminum foil current collector to form alayering or electrode. A porogen may also be added in intervening layersand between layers containing the C—S composite. It may be desirable toadd the porogen in higher concentrations closer to the current collectorto create a gradient in the direction of the thickness of the layeringor electrode. Once the porogen is in place in the formed layering orelectrode, it may then be removed from by washing with dilute acid toleave a void or pore. The type of porogen and the amount can be variedin each layer to control the porosity of the layering or electrode.

Referring again to FIG. 1, depicted is the positive electrode 102, thatmay be formed incorporating a cathode composition as described above.The formed positive electrode 102 may be utilized in the cell 100 inconjunction with a negative electrode, such as the lithium-containingnegative electrode 101 described above. According to differentembodiments, the negative electrode 101 may contain lithium metal or alithium alloy. In another embodiment, the negative electrode 101 maycontain graphite or some other non-lithium material. According to thisembodiment, the positive electrode 102 is formed to include some form oflithium, such as lithium sulfide (Li₂S), and according to thisembodiment, the C—S composite may be lithiated utilizing lithium sulfidewhich is incorporated into the powdered carbon to form the C—Scomposite, instead of elemental sulfur.

A porous separator, such as porous separator 105, may be constructedfrom various materials. As an example, a mat or other porous articlemade from fibers, such as polyimide fibers, which may be used as aporous separator. In another example, using porous laminates made frompolymers such as polyvinylidene fluoride (PVDF), polyvinylidene fluorideco-hexafluoropropylene (PVDF-HFP), polyethylene (PE), polypropylene(PP), and polyimide. In addition, polymers with sufficient functionalityor modifications to promote miscibility with a hydrocarbon ionomer in apolymer blend may also be used in a blend with a hydrocarbon ionomer.

Positive electrode 102, negative electrode 101 and porous separator 105are in contact with a lithium-containing electrolyte medium in the cell100, such as a cell solution with solvent and electrolyte. In thisembodiment, the lithium-containing electrolyte medium is a liquid. Inanother embodiment, the lithium-containing electrolyte medium is asolid. In yet another embodiment, the lithium-containing electrolytemedium is a gel.

Referring to FIG. 2, depicted is a context diagram illustratingproperties 200 of a Li—S battery 201 including a Li—S cell, such as cell100, having a positive electrode including sulfur, such as electrode102. The Li—S cell in Li—S battery 201 incorporates one or morehydrocarbon ionomer articles such as films, membranes, coatings andcompositions, such as described above with respect to cell 100. Thecontext diagram of FIG. 2 demonstrates the properties 200 of the Li—Sbattery 201, having a high coulombic efficiency and high maximumdischarge capacity associated with its discharge. The high coulombicefficiency appears to be directly attributable to the presence of thehydrocarbon ionomer articles in the Li—S cell of Li—S battery 201. FIG.2 also depicts a graph 202 demonstrating maximum discharge capacity percycle of Li—S battery 201 with respect to a number of charge-dischargecycles. The Li—S battery 201 also exhibits high lifetime rechargestability and a high maximum discharge capacity per charge-dischargecycle. All these properties 200 of the Li—S battery 201 are demonstratedin greater detail below through the specific examples.

Referring to FIG. 3, depicted is a coin cell 300 which is operable as anelectrochemical measuring device for testing various configurations andtypes of hydrocarbon ionomer articles. The function and structure of thecoin cell 300 are analogous to those of the cell 100 depicted in FIG. 1.The coin cell 300, like the cell 100, utilizes a lithium-containingelectrolyte medium. The lithium-containing electrolyte medium is incontact with the negative electrode and the positive electrode and maybe a liquid containing solvent and lithium ion electrolyte.

The lithium ion electrolyte may be non-carbon-containing For example,the lithium ion electrolyte may be a lithium salt of such counter ionsas hexachlorophosphate (PF₆ ⁻), perchlorate, chlorate, chlorite,perbromate, bromate, bromite, periodiate, iodate, aluminum fluorides(e.g., AlF₄ ⁻), aluminum chlorides (e.g. Al₂Cl₇ ⁻, and AlCl₄ ⁻),aluminum bromides (e.g., AlBr₄ ⁻), nitrate, nitrite, sulfate, sulfites,permanganate, ruthenate, perruthenate and the polyoxometallates.

In another embodiment, the lithium ion electrolyte may be carboncontaining. For example, the lithium ion salt may contain organiccounter ions such as carbonate, the carboxylates (e.g., formate,acetate, propionate, butyrate, valerate, lactacte, pyruvate, oxalate,malonate, glutarate, adipate, deconoate and the like), the sulfonates(e.g., CH₃SO₃ ⁻, CH₃CH₂SO₃ ⁻, CH₃(CH₂)₂SO₃ ⁻ benzene sulfonate,toluenesulfonate, dodecylbenzene sulfonate and the like. The organiccounter ion may include fluorine atoms. For example, the lithium ionelectrolyte may be a lithium ion salt of such counter anions as thefluorosulfonates (e.g., CF₃SO₃ ⁻, CF₃CF₂SO₃ ⁻, CF₃(CF₂)₂SO₃ ⁻,CHF₂CF₂SO₃ ⁻ and the like), the fluoroalkoxides (e.g., CF₃O—, CF₃CH₂O⁻,CF₃CF₂O⁻ and pentafluorophenolate), the fluoro carboxylates (e.g.trifluoroacetate and pentafluoropropionate) and fluorosulfonimides(e.g., (CF₃SO₂)₂N⁻). Other electrolytes which are suitable for useherein are disclosed in U.S. Published Patent Applications 2010/0035162and 2011/00052998 both of which are incorporated herein by reference intheir entireties.

The electrolyte medium may exclude a protic solvent, since proticliquids are generally reactive with the lithium anode. Solvents arepreferable which may dissolve the electrolyte salt. For instance, thesolvent may include an organic solvent such as polycarbonate, an etheror mixtures thereof. In other embodiments, the electrolyte medium mayinclude a non-polar liquid. Some examples of non-polar liquids includethe liquid hydrocarbons, such as pentane, hexane and the like.

Electrolyte preparations suitable for use in the cell solution mayinclude one or more electrolyte salts in a nonaqueous electrolytecomposition. Suitable electrolyte salts include without limitation:lithium hexafluorophosphate, Li PF₃(CF₂CF₃)₃, lithiumbis(trifluoromethanesulfonyl)imide, lithiumbis(perfluoroethanesulfonyl)imide, lithium(fluorosulfonyl)(nonafluoro-butanesulfonyl)imide, lithium bis(fluorosulfonyl)imide,lithium tetrafluoroborate, lithium perchlorate, lithiumhexafluoroarsenate, lithium trifluoromethanesulfonate, lithiumtris(trifluoromethanesulfonyl)methide, lithium bis(oxalato)borate,lithium difluoro(oxalato)borate, Li₂B₁₂F_(12-x)H_(x) where x is equal to0 to 8, and mixtures of lithium fluoride and anion receptors such asB(OC₆F₅)₃. Mixtures of two or more of these or comparable electrolytesalts can also be used. In one embodiment, the electrolyte salt islithium bis(trifluoromethanesulfonyl)imide). The electrolyte salt may bepresent in the nonaqueous electrolyte composition in an amount of about0.2 to about 2.0 M, more particularly about 0.3 to about 1.5 M, and moreparticularly about 0.5 to about 1.2 M.

EXAMPLES

The following examples demonstrate sample cells with porous separatorscoated with hydrocarbon ionomer as porous separator 306 of coin cell300. Comparative examples A and B demonstrate cells without any articlesincorporating hydrocarbon ionomer. Reference is made to the specificexamples below.

Example 1

Example 1 describes the preparation and electrochemical evaluation of aLi—S cell incorporating a porous separator coated with hydrocarbonionomer which is a lithium exchanged derivative of SURLYN®, a copolymerof ethylene and methacrylate partially neutralized with zinc, sodium,lithium or other metals. The porous separator was coated by spraying itwith SURLYN® and the coated porous separator was immersed in a bathcontaining a lithium ion source for lithium exchange to increase thelithium neutralization in the SURLYN®.

Preparation of C—S Composite:

Approximately 1.0 g of carbon powder (KETJENBLACK EC-600JD, Akzo Nobel)having a surface area of approximately 1400 m²/g BET (Product Data Sheetfor KETJENBLACK EC-600JD, Akzo Nobel) and a pore volume of 4.07 cc/g (asmeasured by the BJH method) was placed in a 30 ml glass vial and loadedinto an autoclave which was charged with approximately 100 grams ofelemental sulfur (Sigma Aldrich 84683). The carbon powder was preventedfrom being in physical contact with the elemental sulfur but the carbonpowder had access to sulfur vapor. The autoclave was closed, purged withnitrogen, and then heated to 300° C. for 24 hours under a staticatmosphere to develop sulfur vapor. The final sulfur content of the C—Scomposite was 51 wt. % sulfur.

Jar Milling of C—S Composite:

1.52 g of the C—S composite described above, 43.2 g of ethanol (SigmaAldrich 459836) and 125 g of 5 mm diameter zirconia media were weighedinto a 125 mL polyethylene bottle. The bottle was sealed, and tumbledend-over-end inside a larger jar on jar mill for 15 hours.

Preparation of Electrode Composition (C—S Composite/Binder/Carbon BlackFormulation):

Polyethylene oxide with average M_(w) of 600,000 (Sigma Aldrich 182028)was dissolved in acetonitrile (Sigma Aldrich 271004) to produce a 5.0wt. % polymer solution. 121 mg of conductive carbon black SUPER C65(Timcal Ltd.) (BET nitrogen surface area of 62 m²/g measured by ASTMD3037-89) (Technical Data Sheet for SUPER C65, Timcal Ltd.) wasdispersed in 3.65 g of the 5.0 wt. % PEO solution, 6.8 g of deionizedwater and 2 g of ethanol. The slurry was mixed with a magnetic stir barfor 15 minutes to form a SUPER C65/PEO slurry. 36 g of the jar milledsuspension of C—S composite described above was added to the SUPERC65/PIB slurry along with 24 g of deionized water. The solid loading inthis mixture has an approximate % PEO in the PEO & C—S of 0.1304 (i.e.,13.04% by weight PEO). This formulation was stirred for 90 minutes, thenmixed for 30 minutes in an ultrasonic bath, and stirred again for 60minutes.

Spray Coating to Form Layering/Electrode:

A layering/electrode was formed by spraying the formulated ink slurrymixture onto one side of double-sided carbon coated aluminum foil (1mil, Exopac Advanced Coatings) as a substrate for thelayering/electrode. The dimensions of the coated area on the substratewas approximately 10 cm×10 cm. The ink slurry mixture was sprayedthrough an air brush (PATRIOT 105, Badger Air-Brush Co.) onto thesubstrate in a layer by layer pattern. The substrate was heated on a 70°C. hotplate for about 10 seconds following the application of every 4layers to the substrate surface. Once all of the ink slurry mixture wassprayed onto the substrate, the layering/electrode was placed in avacuum at a temperature of 70° C. for a period of 5 minutes. The driedlayering/electrode was calendared between two steel rollers on a custombuilt device to a final thickness of about 1 mil.

Preparation of Hydrocarbon Ionomer (SURLYN®) Coated Porous Separator:

A piece of CELGARD 2325 separator (Celgard, LLC) with dimensions 6 cm by11.6 cm was taped to a glass plate and heated to 70° C. on a hot plate.The separator was then sprayed, using the air brush, with an aqueousdispersion of SURLYN® ionomer, 6.4 wt. % loading. When the Surlyn®loading on the separator reached 0.3 mg per cm², the sample was dried ina vacuum oven at 70° C. for 15 minutes. The coated separator was thenion exchanged by immersing it in a bath of aqueous 2M LiOH solutionovernight. It was rinsed with deionized water and dried under vacuum at70° C. for 2 hours.

Preparation of Electrolyte:

2.87 grams of lithium bis(trifluoro-methane sulfonyl)imide (LiTFSI,Novolyte) was combined with 10 milliters of 1,2 dimethoxyethane (glyme,Sigma Aldrich, 259527) to create a 0.9 M electrolyte solution.

Preparation of Coin Cell:

A 14.29 mm diameter circular disk was punched from thelayering/electrode and used as the positive electrode 307. The finalweight of the electrode (14.29 mm in diameter, subtracting the weight ofthe aluminum current collector) was 4.3 mg. This corresponds to acalculated weight of 1.76 mg of elemental sulfur on the electrode.

The coin cell 300 included the positive electrode 307, a 19 mm diametercircular disk was punched from Surlyn®-coated separator sheet describedin the previous section. This disk was soaked overnight in glyme (SigmaAldrich, 259527). The soaked disk was used as the porous separator 306in the coin cell 300 with the coated side of the separator facing thepositive electrode. The positive electrode 307, the separator 306, alithium foil negative electrode 304 (Chemetall Foote Corp.) and a fewelectrolyte drops 305 of the nonaqueous electrolyte was sandwiched in aHohsen 2032 stainless steel coin cell can with a 1 mil thick stainlesssteel spacer disk and wave spring (Hohsen Corp.). The constructioninvolved the following sequence as shown in FIG. 3: bottom cap 308,positive electrode 307, electrolyte drops 305, porous separator 306,electrolyte drops 305, negative electrode 304, spacer disk 303, wavespring 302 and top cap 301. The final assembly was crimped with an MTIcrimper (MTI).

Electrochemical Testing Conditions:

The positive electrode 307 was cycled at room temperature between 1.5and 3.0 V (vs. Li/Li⁰) at C/5 (based on 1675 mAh/g S for the chargecapacity of elemental sulfur). This is equivalent to a current of 335mAh/g S in the positive electrode 307.

Electrochemical evaluation: The maximum charge capacity measured ondischarge at cycle 10 was 827 mAh/g S with a coulombic efficiency of80.2%.

Example 2

The materials in example 2 were prepared as identical to those inexample 1, except the hydrocarbon ionomer coated porous separator wascalendared at a higher temperature before the cell was assembled.

Preparation of Hydrocarbon Ionomer (SURLYN®) Coated Porous Separator:

A strip of the lithium ion exchanged SURLYN® coated separator, 6 cm×3cm, was cut from the separator in Example 1 and calendared between twosteel rollers on a custom-built calendaring device. The separator wassandwiched between pieces of KAPTON film. The temperature of the rollerswas maintained at 70° C.

Preparation of Coin Cell:

A coin cell and electrolyte were prepared and cycled using the sameprocedures as example 1. The final weight of the electrode (14.29 mm indiameter, subtracting the weight of the aluminum current collector) was4.1 mg. This corresponds to a calculated weight of 1.68 mg of elementalsulfur on the electrode.

Electrochemical Testing Conditions:

The positive electrode 307 was cycled at room temperature between 1.5and 3.0 V (vs. Li/Li⁰) at C/5 (based on 1675 mAh/g S for the chargecapacity of elemental sulfur). This is equivalent to a current of 335mAh/g S in the positive electrode 307.

Electrochemical Evaluation:

The maximum charge capacity measured on discharge at cycle 10 was 855mAh/g S with a coulombic efficiency of 90%.

Comparative Example A

Comparative example A describes the preparation and electrochemicalevaluation of a Li—S cell with a porous separator not coated with anyhydrocarbon ionomer for comparison with examples 1 and 2 above. The Li—Scell in comparative example A utilizes a porous separator that is notcoated with any hydrocarbon ionomer or calendared at any temperature,but was otherwise prepared in a manner similar to the preparationdescribed in examples 1 and 2 above.

Preparation of Coin Cell:

A coin cell was prepared and cycled using the same procedures asexamples 1 and 2. The positive electrode 307 used in comparative exampleA was identical to the electrodes in examples 1 and 2. The final weightof the electrode (14.29 mm in diameter, subtracting the weight of thealuminum current collector) was 4.8 mg. This corresponds to a calculatedweight of 2.0 mg of sulfur on the electrode. The porous separator wasmade from CELGARD 2325, which was used as received. The porous separatorwas not soaked in glyme prior to assembling the coin cell.

Electrochemical Testing Conditions:

The positive electrode 307 was cycled at room temperature between 1.5and 3.0 V (vs. Li/Li⁰) at C/5 (based on 1675 mAh/g S for the chargecapacity of elemental sulfur). This is equivalent to a current of 335mAh/g S in the positive electrode 307.

Electrochemical Evaluation:

The maximum charge capacity measured on discharge at cycle 10 was 1,056mAh/g S with a coulombic efficiency of 51.3%.

Example 3

Example 3 describes the preparation and electrochemical evaluation of aLi—S cell including a porous separator coated with a hydrocarbon ionomerthat is a lithium exchanged derivative of a sodium salt of polyvinylsulfonic acid (PVSA) (Sigma Aldrich, 278424).

Preparation of C—S Composite:

Approximately 1.0 g of carbon powder (KETJENBLACK EC-600JD, Akzo Nobel)having a surface area of approximately 1400 m²/g BET (Product Data Sheetfor KETJENBLACK EC-600JD, Akzo Nobel) and a pore volume of 4.07 cc/g (asmeasured by the BJH method) was placed in a 30 ml glass vial and loadedinto an autoclave which was charged with approximately 100 grams ofelemental sulfur (Sigma Aldrich 84683). The carbon powder was preventedfrom being in physical contact with the elemental sulfur but the carbonpowder had access to sulfur vapor. The autoclave was closed, purged withnitrogen, and then heated to 300° C. for 24 hours under a staticatmosphere to develop sulfur vapor. The final sulfur content of the C—Scomposite was 51 wt. % sulfur.

Jar Milling of C—S Composite:

1.8 g of the C—S composite described above, 51 g of toluene (EMDChemicals) and 120 g of 5 mm diameter zirconia media was weighted into a125 mL polyethylene bottle. The bottle was sealed, and tumbledend-over-end inside a larger jar on jar mill for 15 hours.

Preparation of Base Composition (C—S Composite/Binder/Carbon BlackFormulation):

Polyisobutylene with average M_(w) of 4,200,000 (Sigma Aldrich 181498)was dissolved in toluene to produce a 2.0 wt. % polymer solution. 153 mgof conductive carbon black SUPER C65 (Timcal Ltd.) (BET nitrogen surfacearea of 62 m²/g measured by ASTM D3037-89) (Technical Data Sheet forSUPER C65, Timcal Ltd.) was dispersed in 11.4 g of the 2.0 wt. % PIBsolution. 45 g of the jar milled suspension of C—S composite describedabove was added to the SUPER C65/PIB slurry along with 27 g of tolueneto form an ink slurry with about 2 wt. % solid loading. This ink wasstirred for 3 hours.

Spray Coating to Form Layering/Electrode:

A layering/electrode was formed by spraying the formulated ink slurryonto one side of double-sided carbon coated aluminum foil (1 mil, ExopacAdvanced Coatings) as a substrate for the base layering/electrode. Thedimensions of the coated area on the substrate was approximately 10cm×10 cm. The ink slurry was sprayed through an air brush (PATRIOT 105,Badger Air-Brush Co.) onto the substrate in a layer by layer pattern.The substrate was heated on a 70° C. hotplate for about 10 secondsfollowing the application of every 4 layers to the substrate surface.Once all of the ink slurry was sprayed onto the substrate, the baselayering/electrode was placed in a vacuum at a temperature of 70° C. fora period of 5 minutes.

Preparation of Hydrocarbon Ionomer (PVSA) Solution:

A 25 wt. % dispersion of polyvinylsulfonic acid (PVSA) sodium salt(Sigma Aldrich, 278424) was passed through a column of DOWEX® (Dow50WX8-200) ion exchange resin which had been exchanged with lithiumions. The polymer concentration in the eluate solution was 2.5 wt. %.

Hydrocarbon Ionomer (PVSA) Spray Coating of Porous Separator:

A piece of CELGARD 2325 separator (Celgard, LLC) with dimensions 6 cm by9 cm was taped to a glass plate and heated to 70° C. on a hot plate. Theporous separator was then sprayed using the air brush with the PVSAsolution prepared in the previous section. When the PVSA loading on theseparator reached about 0.7 mg per square cm, the sample was dried in avacuum oven at 70° C. overnight. The coated separator was transferred toa nitrogen dry box.

Preparation of Electrolyte:

2.87 grams of lithium bis(trifluoro-methane sulfonyl)imide (LiTFSI,Novolyte) was combined with 10 milliters of 1,2 dimethoxyethane (glyme,Sigma Aldrich, 259527) to create a 0.9 M electrolyte solution.

Preparation of Coin Cell:

A coin cell 300 was prepared using electrode and the coated porousseparator described above for testing. A 14.29 mm diameter circular diskwas punched from the final layering/electrode and used as the positiveelectrode 307. The final weight of the electrode (14.29 mm in diameter,subtracting the weight of the aluminum current collector) was 5.7 mg.This corresponds to a calculated weight of 2.34 mg of elemental sulfuron the electrode.

A 19 mm diameter circular disk was punched from the PVSA-coatedseparator sheet described in the previous section. This disk was soakedovernight in glyme (Sigma Aldrich, 259527). It was then used as theporous separator 306 in the coin cell 300 with the coated side of theseparator facing the positive electrode 307.

The positive electrode 307, the separator 306, a lithium foil negativeelectrode 304 (Chemetall Foote Corp.) and a few electrolyte drops 305 ofthe nonaqueous electrolyte were sandwiched in a Hohsen 2032 stainlesssteel coin cell can with a 1 mil thick stainless steel spacer disk andwave spring (Hohsen Corp.). The construction involved the followingsequence as shown in FIG. 3: bottom cap 308, positive electrode 307,electrolyte drops 305, porous separator 306, electrolyte drops 305,negative electrode 304, spacer disk 303, wave spring 302 and top cap301. The final assembly was crimped with an MTI crimper (MTI).

Electrochemical Testing Conditions:

The positive electrode 307 was cycled at room temperature between 1.5and 3.0 V (vs. Li/Li⁰) at C/5 (based on 1675 mAh/g S for the chargecapacity of elemental sulfur). This is equivalent to a current of 335mAh/g S in the positive electrode 307.

Electrochemical Evaluation:

The maximum charge capacity measured on discharge at cycle 10 was 1,002mAh/g S with a coulombic efficiency of 83.6%.

Example 4

Example 4 describes the preparation and electrochemical evaluation of aLi—S cell including a porous separator coated with hydrocarbon ionomerwhich was a lithium exchanged sulfonated derivative (SPEEK) of apoly(ether ether-ketone) PEEK (Victrex, 150P). The positive electrode inthis example was identical to the electrode used in example 3. Theseparator in this example was coated with sulfonated poly(ether etherketone) (SPEEK) ionomer instead of PVSA.

Sulfonation of PEEK with Lithium Ion Exchange Forming SPEEK:

5.0 g of PEEK (Victrex, 150P, Lancashire, UK) was dissolved in 176 g ofconcentrated sulfuric acid, and stirred rapidly for six days at roomtemperature. The polymer was precipitated from solution in ice water,then filtered and rinsed with deionized water until the filtrate pHreached 4. The polymer was exchanged with lithium ions by stirring in abath of 2 M lithium hydroxide. The solution was filtered and the polymerwas rinsed with deionized water until the filtrate was pH neutral.Finally the polymer was dried in a 70° C. vacuum oven overnight.

Hydrocarbon Ionomer (SPEEK) Spray Coating of Porous Separator:

Lithium-exchanged SPEEK was dissolved in dimethylacetimide (DMAc) (SigmaAldrich, 271012) at a 5 wt. % concentration. A piece of CELGARD 2325porous separator (Celgard, LLC) with dimensions 6 cm by 6 cm was tapedto glass plate and heated to 70° C. on a hot plate. The porous separatorwas then spray coated, using the air brush, with the lithium-exchangedSPEEK solution. When the ionomer loading on the separator reached about0.2 mg per square cm, the sample was transferred to a 70° C. vacuum ovenfor 8 hours. The coated separator was transferred to a nitrogen dry box.

Preparation of Electrolyte:

2.87 grams of lithium bis(trifluoro-methane sulfonyl)imide (LiTFSI,Novolyte) is combined with 10 milliters of 1,2 dimethoxyethane (glyme,Sigma Aldrich, 259527) to create a 0.9 M electrolyte solution.

Preparation of Coin Cell:

Coin cells were prepared and cycled using the same procedures asexample 1. The final weight of the electrode (14.29 mm in diameter,subtracting the weight of the aluminum current collector) was 4.9 mg.This corresponds to a calculated weight of 2.01 mg of sulfur on theelectrode.

Electrochemical Testing Conditions:

The positive electrode 307 is cycled at room temperature between 1.5 and3.0 V (vs. Li/Li⁰) at C/5 (based on 1675 mAh/g S for the charge capacityof elemental sulfur). This is equivalent to a current of 335 mAh/g S inthe positive electrode 307.

Electrochemical Evaluation:

The maximum charge capacity measured on discharge at cycle 10 was 945mAh/g S with a coulombic efficiency of 92.3%.

Comparative Example B

Comparative example B describes the preparation and electrochemicalevaluation of a Li—S cell with a porous separator not coated with anyhydrocarbon ionomer for comparison with examples 3 and 4 above. The Li—Scell in comparative example B utilizes a porous separator that is notcoated with any hydrocarbon ionomer.

Preparation of Coin Cell:

A coin cell was prepared and cycled using the same procedures asexamples 3 and 4. The positive electrode 307 used in comparative exampleB was identical to the electrode in examples 3 and 4. The final weightof the electrode (14.29 mm in diameter, subtracting the weight of thealuminum current collector) was 5.2 mg. This corresponds to a calculatedweight of 2.09 mg of sulfur on the electrode. The porous separator wasmade from CELGARD 2325, which was used as received. The porous separatorwas not soaked in glyme prior to assembling the coin cell.

Electrochemical Testing Conditions:

The positive electrode 307 was cycled at room temperature between 1.5and 3.0 V (vs. Li/Li⁰) at C/5 (based on 1675 mAh/g S for the chargecapacity of elemental sulfur). This is equivalent to a current of 335mAh/g S in the positive electrode 307.

Electrochemical Evaluation:

The maximum charge capacity measured on discharge at cycle 10 was 1,023mAh/g S with a coulombic efficiency of 56.5%.

Example 5

Example 5 describes the preparation and electrochemical evaluation of aLi—S cell incorporating a porous separator coated with hydrocarbonionomer which is a lithium exchanged derivative of SURLYN®, a copolymerof ethylene and methacrylate partially neutralized with zinc, sodium,lithium or other metals. The porous separator was coated by spraying itwith SURLYN® and the coated porous separator was immersed in a bathcontaining a lithium ion source for lithium exchange to increase thelithium neutralization in the SURLYN®.

Preparation of C—S Composite:

Approximately 1.0 g of carbon powder (KETJENBLACK EC-600JD, Akzo Nobel)having a surface area of approximately 1400 m2/g BET (Product Data Sheetfor KETJENBLACK EC-600JD, Akzo Nobel) and a pore volume of 4.07 cc/g (asmeasured by the BJH method) was placed in a 30 ml glass vial and loadedinto an autoclave which was charged with approximately 100 grams ofelemental sulfur (Sigma Aldrich 84683). The carbon powder was preventedfrom being in physical contact with the elemental sulfur but the carbonpowder had access to sulfur vapor. The autoclave was closed, purged withnitrogen, and then heated to 300° C. for 24 hours under a staticatmosphere to develop sulfur vapor. The final sulfur content of the C—Scomposite was 53.3 wt. % sulfur.

Jar Milling of C—S Composite:

1.85 g of the C—S composite described above, 53.15 g of toluene (EMDChemicals) and 115 g of 5 mm diameter zirconia media were weighed into a125 mL polyethylene bottle. The bottle was sealed, and tumbledend-over-end inside a larger jar on jar mill for 15 hours.

Preparation of (80/12/8) Electrode Composition (C—SComposite/Binder/Carbon Black Formulation):

Polyisobutylene with average Mw of 4,200,000 (Sigma Aldrich 1814980 wasdissolved in toluene to produce a 2.0 wt. % polymer solution. 290 mg ofconductive carbon black SUPER C65 (Timcal Ltd.) (BET nitrogen surfacearea of 62 m²/g measured by ASTM D3037-89) (Technical Data Sheet forSUPER C65, Timcal Ltd.) was dispersed in 21.65 g of the 2.0 wt. % PIBsolution along with 21 g of toluene. The slurry was mixed with amagnetic stir bar for 5 minutes to form a SUPER C65/PIB slurry. 2.912 gof the jar milled suspension of C—S composite described above was addedto the SUPER C65/PIB slurry along with an additional 44 g of toluene.This ink, with a 2.10 wt. % solid loading, was stirred for 3 hours.

Spray Coating to Form Layering/Electrode:

A layering/electrode was formed by spraying the formulated ink slurrymixture onto one side of double-sided carbon coated aluminum foil (1mil, Exopac Advanced Coatings) as a substrate for thelayering/electrode. The dimensions of the coated area on the substratewas approximately 5 cm×5 cm. The ink slurry mixture was sprayed throughan air brush (PATRIOT 105, Badger Air-Brush Co.) onto the substrate in alayer by layer pattern. The substrate was heated on a 70° C. hotplatefor about 10 seconds following the application of every 4 layers to thesubstrate surface. Once all of the ink slurry mixture was sprayed ontothe substrate, the layering/electrode was placed in a vacuum at atemperature of 70° C. for a period of 5 minutes. The driedlayering/electrode was calendared between two steel rollers on a custombuilt device to a final thickness of about 1 mil.

Preparation of Hydrocarbon Ionomer (SURLYN®) Coated Energain® PolyimideBattery Separator:

A piece of Energain® Polyimide Battery Separator (DuPont Company) withdimensions 10.7 cm by 6.7 cm was taped to a glass plate and heated to70° C. on a hot plate. The separator was then sprayed, using the airbrush, with an aqueous dispersion of SURLYN® ionomer, 6.4 wt. % loading.When the Surlyn® loading on the separator reached 0.4 mg per cm², thesample was dried in a vacuum oven at 70° C. for 15 minutes. The coatedseparator was then ion exchanged by immersing it in a bath of aqueous 2MLiOH solution overnight. It was rinsed with deionized water and driedunder vacuum at 70° C. for 2 hours. After drying overnight at 70 C, a2.25″×2.15″ piece of the Surlyn®/Energain® composite was hot pressed ona Carver hyraulic press. The hydraulic press was preheated to 70 C. Thecomposite was sandwiched between two PFA (perfluoroalkyl) sheets andthen sandwiched between two pieces of 4″×4″ glass plate. 1000 poundsforce was applied for 10 minutes to create the final compositestructure.

Scanning electron micrographs of the polymer composite were obtained byfirst cutting approximately 0.5 cm×1.0 cm section film and mounting iton sticky carbon tape on an Si wafer. The mounted films were coated with2 nm Os metal using the OPC-80 Osmium Plasma Coater. The films wereexamined in the Hitachi 54000 FE-SEM at 2.5 keV accelerating voltage ata 10 mm working distance. Images were taken at very low magnifications(100×) to moderately high magnification (10,000×) to compare surfacefeatures.

Preparation of Electrolyte:

3.59 grams of lithium bis(trifluoro-methane sulfonyl)imide (LiTFSI,Novolyte) was combined with 20.32 grams (23.40 ml) of 1,2dimethoxyethane (glyme, Sigma Aldrich, 259527) to create a 0.5 Melectrolyte solution.

Preparation of Coin Cell:

A 14.29 mm diameter circular disk was punched from thelayering/electrode and used as the positive electrode 307. The finalweight of the electrode (14.29 mm in diameter, subtracting the weight ofthe aluminum current collector) was 4.71 mg. This corresponds to acalculated weight of 2.01 mg of elemental sulfur on the electrode.

The coin cell 300 includes the positive electrode 307, the 19 mmdiameter circular disk punched from the Surlyn®/Energain® compositedescribed in the previous section and two 19 mm piece of Celgard 2500polyolefin separator (Celgard, LLC). The two Celgard 2500 diskes wereused to sandwich the Surlyn®/Energain® compous, and were used togetheras the final separator 306 in the coin cell 300 with the lithiumexchanged The Surlyn®/Energain®composite was assembled so the “Surlyn”side of the separator faced the positive electrode. The positiveelectrode 307, the separator 306, a lithium foil negative electrode 304(3 mils thickness, Chemetall Foote Corp.) and a few electrolyte drops305 of the nonaqueous electrolyte was sandwiched in a MTI stainlesssteel coin cell can with a 1 mil thick stainless steel spacer disk andwave spring (Hohsen Corp.). The construction involved the followingsequence as shown in FIG. 3: bottom cap 308, positive electrode 307,electrolyte drops 305, separator 306, electrolyte drops 305, negativeelectrode 304, spacer disk 303, wave spring 302 and top cap 301. Thefinal assembly was crimped with an MTI crimper (MTI).

Electrochemical Testing Conditions:

The positive electrode 307 was cycled at room temperature between 1.5and 3.0 V (vs. Li/Li⁰) at C/5 (based on 1675 mAh/g S for the chargecapacity of elemental sulfur). This is equivalent to a current of 335mAh/g S in the positive electrode 307.

Electrochemical Evaluation:

The maximum charge capacity measured on discharge at cycle 10 was 1013mAh/g S with a coulombic efficiency of 90%.

Utilizing a Li—S cell incorporating hydrocarbon ionomer articles, suchas coatings, membranes, films and other articles incorporatinghydrocarbon ionomer provides a high maximum charge capacity Li—S batterywith high coulombic efficiency. Li—S cells incorporating hydrocarbonionomer articles may be utilized in a broad range of Li—S batteryapplications in providing a source of potential power for many householdand industrial applications. The Li—S batteries incorporating thesehydrocarbon ionomer articles are especially useful as power sources forsmall electrical devices such as cellular phones, cameras and portablecomputing devices and may also be used as power sources for car ignitionbatteries and for electrified cars.

Although described specifically throughout the entirety of thedisclosure, the representative examples have utility over a wide rangeof applications, and the above discussion is not intended and should notbe construed to be limiting. The terms, descriptions and figures usedherein are set forth by way of illustration only and are not meant aslimitations. Those skilled in the art recognize that many variations arepossible within the spirit and scope of the principles of the invention.While the examples have been described with reference to the figures,those skilled in the art are able to make various modifications to thedescribed examples without departing from the scope of the followingclaims, and their equivalents.

Further, the purpose of the foregoing Abstract is to enable the U.S.Patent and Trademark Office and the public generally and especially thescientists, engineers and practitioners in the relevant art who are notfamiliar with patent or legal terms or phraseology, to determine quicklyfrom a cursory inspection the nature and essence of this technicaldisclosure. The Abstract is not intended to be limiting as to the scopeof the present invention in any way.

What is claimed is:
 1. A cell, comprising: a positive electrode comprising sulfur compound; a negative electrode; a circuit coupling the positive electrode with the negative electrode; an electrolyte medium; an interior wall of the cell; and an article comprising a hydrocarbon ionomer.
 2. The cell of claim 1, wherein the article is a porous separator comprising at least one of polyimide, polyethylene and polypropylene.
 3. The cell of claim 1, wherein the hydrocarbon ionomer is incorporated as a surface coating on a surface of the article in an amount of about 0.0001 to 100 mg/cm².
 4. The cell of claim 2, wherein the hydrocarbon ionomer is located in a pore wall of a pore in the porous separator and exposed to electrolyte medium in a pore volume in the pore.
 5. The cell of claim 1, wherein the electrolyte medium is a lithium-containing cell solution comprising solvent and electrolyte.
 6. The cell of claim 1, wherein the article is a coating located on a surface of at least one of a porous separator, the negative electrode, the circuit, and the interior wall of the cell.
 7. The cell of claim 1, wherein the hydrocarbon ionomer comprises at least one ionic group selected from carboxylate ionic groups.
 8. The cell of claim 1, wherein the hydrocarbon ionomer is a random copolymer of poly(ethylene-co-(meth)acrylic) acid, and wherein the copolymer is at least partially neutralized and comprises (meth)acrylic acid comonomer that is one of acrylic acid comonomer, methacrylic acid comonomer, and a combination of acrylic acid and methacrylic acid comonomers.
 9. A method for making a cell, comprising: fabricating a plurality of components to form the cell, wherein the plurality comprises a positive electrode comprising sulfur compound, a negative electrode, a circuit coupling the positive electrode with the negative electrode, an electrolyte medium, an interior wall of the cell, and an article comprising a hydrocarbon ionomer.
 10. The method of claim 9, wherein the article is a porous separator comprising at least one of polyimide, polyethylene and polypropylene.
 11. The method of claim 9, wherein the hydrocarbon ionomer comprises at least one ionic group selected from carboxylate ionic groups.
 12. A method for using a cell, comprising at least one step from the plurality of steps comprising converting chemical energy stored in the cell into electrical energy; and converting electrical energy into chemical energy stored in the cell, wherein the cell comprises a positive electrode comprising sulfur compound, a negative electrode, a circuit coupling the positive electrode with the negative electrode, an electrolyte medium, an interior wall of the cell, and an article comprising hydrocarbon ionomer.
 13. The method of claim 12, wherein the cell is associated with at least one of a portable battery, a power source for an electrified vehicle, a power source for an ignition system of a vehicle and a power source for a mobile device.
 14. The method of claim 12, wherein the article is a porous separator comprising at least one of polyimide, polyethylene and polypropylene.
 15. The method of claim 12, wherein the hydrocarbon ionomer comprises at least one ionic group selected from carboxylate ionic groups. 